src/include/nodes/value.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * value.h
   4  *        interface for Value nodes
   5  *
   6  *
   7  * Copyright (c) 2003-2008, PostgreSQL Global Development Group
   8  *
   9  * $PostgreSQL$
  10  *
  11  *-------------------------------------------------------------------------
  12  */
  13
  14 #ifndef VALUE_H
  15 #define VALUE_H
  16
  17 #include "nodes/nodes.h"
  18
  19 /*----------------------
  20  *              Value node
  21  *
  22  * The same Value struct is used for five node types: T_Integer,
  23  * T_Float, T_String, T_BitString, T_Null.
  24  *
  25  * Integral values are actually represented by a machine integer,
  26  * but both floats and strings are represented as strings.
  27  * Using T_Float as the node type simply indicates that
  28  * the contents of the string look like a valid numeric literal.
  29  *
  30  * (Before Postgres 7.0, we used a double to represent T_Float,
  31  * but that creates loss-of-precision problems when the value is
  32  * ultimately destined to be converted to NUMERIC.      Since Value nodes
  33  * are only used in the parsing process, not for runtime data, it's
  34  * better to use the more general representation.)
  35  *
  36  * Note that an integer-looking string will get lexed as T_Float if
  37  * the value is too large to fit in a 'long'.
  38  *
  39  * Nulls, of course, don't need the value part at all.
  40  *----------------------
  41  */
  42 typedef struct Value
  43 {
  44         NodeTag         type;                   /* tag appropriately (eg. T_String) */
  45         union ValUnion
  46         {
  47                 long            ival;           /* machine integer */
  48                 char       *str;                /* string */
  49         }                       val;
  50 } Value;
  51
  52 #define intVal(v)               (((Value *)(v))->val.ival)
  53 #define floatVal(v)             atof(((Value *)(v))->val.str)
  54 #define strVal(v)               (((Value *)(v))->val.str)
  55
  56 extern Value *makeInteger(long i);
  57 extern Value *makeFloat(char *numericStr);
  58 extern Value *makeString(char *str);
  59 extern Value *makeBitString(char *str);
  60
  61 #endif   /* VALUE_H */